1. Field of the Invention
The present invention relates to golf clubs. More specifically, the present invention relates to a sole plate for a golf club head.
2. Description of the Related Art
In general, a golf club head has four components: a face, a crown, a sole and a hosel for receiving a shaft. The sole has a greater affect on the club head performance in a driver or fairway than in an iron or putter. Also, as golf club heads have increased in volume, the sole has been modified to maintain or increase the performance of these larger golf club heads.
The prior art of sole variations for woods and utility clubs is fairly limited. It is reported by Jeffrey Ellis on page 263 of his book, The Clubmaker's Art, that the convex sole for a golf club head was invented by Willie Dunn, Jr., for which Dunn received British Patent Number 22,574 in 1891. Dunn's convex sole was an improvement over the flat soles of the time. Another development in golf club soles was Crankshaw, U.S. Pat. No. 1,619,566 for a "V" sole that has its apex on the centerline of the driving face. Another example is Grieve, U.S. Pat. No. 1,868,286, for a golf club sole that had a "T" shaped metal ridge. Yet another example is Thompson, U.S. Pat. No. 3,761,095 for a Golf Club Head With Sole Plate-Keel Attachment, filed in 1972, and which was assigned to Callaway Golf. The Thompson utility club, marketed under the name, GINTY.RTM., was directed to minimizing the ground contact area through use of the keel. A further example is Crow, U.S. Pat. No. 4,332,388 which was filed in 1980 for a golf club with a metal sole plate that has a pair of parallel runners to skid on the ground surface with minimum penetration. Although there were variations in the sole of persimmon woods, as evidenced by the above, the vast majority of persimmon woods had relatively flat soles.
One of the first metal woods to have a variation in its sole was the Callaway Golf S2H2.RTM. golf club, set forth in Helmsetter, U.S. Pat. No. Des 318,087, filed in February of 1989 for a sole with four facets on a golf club head that had a volume of less than 190 cubic centimeters.
Another metal wood sole is the WARBIRD.RTM. sole of the GREAT BIG BERTHA.RTM. driver that was sold by Callaway Golf, and as set forth in U.S. Pat. No. 5,240,252, filed in January of 1992. The WARBIRD.RTM. sole had a medial ridge defining two concave side recesses and also had a concave rear recess to lessen the drag forces during a golf swing and to strengthen the sole walls.
Another sole is set forth in Gorman, U.S. Pat. No. 5,314,185. The Gorman patent discloses a sole with two parallel struts to raise the center of gravity. Dumontier, et al., U.S. Pat. No. 5,547,188, discloses a sole that has a rib with two diverging branches and an attack edge, and where the branches change divergence width with changes in the loft angles. Dekura, U.S. Pat. No. 5,573,469, originally filed in Japan in 1994, discloses a sole with a convex portion for stability during address so that the face may be properly oriented for striking a golf ball. McCabe, et al., U.S. Pat. No. Des 402,726 discloses a sole that has two recesses nearest the rear. Imai, U.S. Pat. No. 6,056,649, originally filed in Japan in 1997, discloses a sole with two weighted protrusions for lowering the center of gravity.
Another distinctive sole is the sole of the GREAT BIG BERTHA.RTM. HAWK EYE.RTM. golf club, and as set forth in Helmstetter, U.S. Pat. No. 6,007,433, filed in April of 1998. The HAWK EYE.RTM. sole has a medial ridge with two lateral extensions that define two downwardly convex recesses. Other soles that have some relation to the above-mentioned prior art are set forth in U.S. Trademark Registrations 1947849, 1922181, 1918108, 2300297, 2046904, and 2013319.
However, there remains a need for a sole for new golf club heads due to the increased volume of golf club heads, and the high performance nature of golf club heads (as measured by driver distance). The prior art soles, although adequate and performance enhancing, do not optimize the benefits of a high performance, large volume golf club head.